Vault and safe structures are utilized in a variety of applications to provide protection and safe keeping for valuable items, such as money, jewelry, confidential records and important documents. In addition to permanent vaults and safes of the monolithic type, like those often found in banks, some of the vault and safe structures used today are modular structures having multiple, detachable panels which are readily assembled to form the vault or safe. Modular vaults can be disassembled after a particular use and moved elsewhere, as necessary.
In the past, materials such as steel and concrete have been chosen for vault structures due to their characteristic strength and penetration resistance to a large variety of penetration devices. However, safe and vault structures made of steel or concrete or a combination thereof, are heavy and oftentimes difficult and time consuming to build or install. When the vault structure is modular and the vault panels are periodically assembled and dissembled, the difficulty with heavy materials such as steel and concrete is exacerbated. Additionally, since many vault structures today are used on the upper levels of high rise buildings, weight is an important factor in the overall desirability of the vault structure.
To achieve lighter vault panels, materials other than steel or concrete may be used. In the past, lighter panel material has meant a reduction in the penetration resistance achieved by the panel. However, not all vault structures are required to withstand prolonged penetration attempts by burglars. Many vault structures are utilized in areas which are under the surveillance of security personnel or otherwise protected by an electronic security system. Therefore, in these cases, the vault is sufficient if it deters a prospective burglar for the maximum time period necessary for the security personnel to observe the break-in attempt or for the alarm system to be triggered. To this end, modular vault structures are rated by Underwriter's Laboratories (UL), such as in test UL608 for Burglary Resistance Vault Doors and Panels, according to the amount of time that is necessary to breach the integrity of the vault panels and gain access to the internal chamber of the vault. For example, a UL rating of CLASS M is given to a modular vault panel which can withstand a break-in attempt for approximately 15 minutes, while ratings of Class 1, 2 and 3 correspond to a panel that can deter penetration for approximately 1/2, 1 and 2 hours, respectively. Successful penetration of a vault panel under U.L. standards is determined by the time it takes to make a hole in the panel of a size sufficient to allow the passage of an average human being through the opening, approximately 96 square inches. Modular vault structures are rated for a variety of cutting and torching tools, and greater or lesser penetration times are given other Class ratings.
Modular vault structures are usually composed of panels which fit together at their edges to create the walls, ceiling and sometimes floors of the vault. In modular vaults it is desirable to have panels which are dimensioned so as to be easily movable and sufficiently lightweight so allowing assembly and disassembly without the need for heavy machinery. While panels made of steel and concrete may sufficiently withstand penetration attempts for the desired time period, their increased weight and decreased mobility often makes them unsatisfactory for use in particular modular vault applications. It is therefore an objective of this invention to produce a lightweight modular vault panel which may be manufactured relatively inexpensively and will withstand attempts sufficiently to obtain the desired UL rating or a similar industry rating.
One prior art way of achieving a lightweight panel is to provide a multi-layered panel made of layers of wood overlying each other and joined together by nails or other fasteners. A typical example of such a structure is shown in Fee, et al. U.S. Pat. No. 4,918,900 where 2".times." boards are stacked and successively nailed together to form the main layer of the vault panel, while surface sheets are laid over the stack and secured thereto. The Fee panel uses a plurality of nails to interconnect the adjacent boards in the stack. The nails in the stack are also useful in resisting penetration attempts with sawing devices. However, since the nails extend essentially parallel to the main face of the panel and are spaced from one another in a repetitive grid, it is possible to make a cut through the panel without ever striking a nail. Additionally, the stack of 2".thrfore.4" boards has layers of wood with grains extending in the same direction, thus making chipping around the nails and through the panel a simpler task. Furthermore, the Fee panel shows metal interspersed between the boards of the stalk making the panel more susceptible to attacks with a cutting torch because the metal enhances the operation of the torch by dispersing the heat of the torch uniformly over the entire body of the panel.
Consequently, it is an objective of the present invention to provide an improved lightweight, multi-layered wood panel for a modular vault structure which provides enhanced penetration protection over known wood panels. The panel should provide penetration resistance of both cutting and torching tools. Further, it is an objective to provide a panel where repetitiveness in its construction does not detrimentally affect the operation of the panel.